Differential Chaos Shift Keying Modulation Research Articles

DPI DCSK Modulation with BCJR Decoding

This paper proposes a novel [Formula: see text]-ary differential permutation index (DPI) differential chaos shift keying (DCSK) by using the Bahl–Cocke–Jeline–Raviv (BCJR) decoding (DPI-DCSK-BCJR) for chaos-based communications. By exploiting the characteristics of differential modulation and quasi-orthogonality of chaotic signals, the proposed DPI-DCSK-BCJR can provide two more calculated energies to decide the transmitted bits. Theoretical analysis of bit-error-rate (BER) is carried out over multipath Rayleigh fading channel and then validated via simulations. The proposed scheme is demonstrated to outperform the conventional DPI-DCSK by 2[Formula: see text]dB for different [Formula: see text]. This performance gain is especially increased over high-delay channels. Furthermore, the advantage of the proposed frequency-modulated DPI-DCSK-BCJR is verified over practical ultra-wideband (UWB) wireless channels. In addition, we investigate the proposed DPI-DCSK-BCJR for more generalized multiuser communications. The simulation result shows that DPI-DCSK-BCJR can achieve performance gains up to 5[Formula: see text]dB as compared to the conventional PI-DCSK and DPI-DCSK for both two and three user systems. Consequently, the proposed DPI-DCSK-BCJR can be considered as a low-cost alternative for low-complexity and high-rate chaotic-based wireless communication.

A Novel Multi-User Carrier Index Differential Chaos Shift Keying Modulation Scheme

In this paper, a novel multi-user carrier index differential chaos shift keying (MU CI-DCSK) modulation scheme is proposed. For a better utilization of spectrum resources, each user is allocated a private subcarrier for reference signal transmission, while the remaining subcarriers are public and shared by all users to transmit their own data-bearing signals. To avoid user interferences in this design, users are distinguished in a code division multiple access (CDMA) way based on Walsh codes. By exploiting the redundancies in the transmitted signals, repeated segments of received signals are averaged, leading to greatly reduced noises and a noticeable improvement in bit error rate (BER) performance. BER expressions of this new system are derived over the additive white Gaussian noise (AWGN) and multi-path Rayleigh fading channels. Simulation results and comparisons are performed to verify the feasibility and advantages of this new scheme.

Double-Stream Differential Chaos Shift Keying Communications Exploiting Chaotic Shape Forming Filter and Sequence Mapping

A new Differential Chaos Shift Keying modulation scheme exploiting Chaotic Shape-forming Filter and Sequence Mapping (CSF-SM-DCSK) is being proposed. The new CSF-SM-DCSK system employs a novel sequence mapping rule and includes a data correction module to achieve a good trade-off between the low Bit Error Rate (BER) performance and high transmission rate. It transmits two data streams simultaneously and preserves the simplicity and robustness of DCSK method. Channel one, transmitting a Low Priority Stream (LPS), generates the chaotic carrier by a Chaotic Shape-forming Filter (CSF) at the transmitter and applies a coherent Matched Filter (MF) at the receiver to recover the information. Channel two, transmitting a High Priority Stream (HPS), relies on conventional DCSK modulation, while the reference and information-bearing parts are transmitted simultaneously with orthogonal sine and cosine carriers. This double-stream solution eliminates the need for analog RF delay lines and doubles the data transmission rate. Before feeding the LPS data stream into the modulator, each LPS bit is encoded into a symbol sequence using sequence mapping. This approach, together with the coherent MF reception, equips the LPS channel with an extremely high robustness against channel noise and multipath propagation. To handle every possible redundancy in the received signal and to minimize the possibility of making wrong decisions, a data correction block is also introduced. Initially, a rough estimation of the received HPS DCSK bit is done at the receiver, then this estimation is used to remove the DCSK modulation from the received information-bearing signal. The three inputs of data correction blocks are: (i) the reference and (ii) the information-bearing parts of the received signal in their original form, and (iii) the received information-bearing signal where the DCSK modulation is removed. The data correction block improves the BER performance while the increased channel capacity, enabled by the double-stream approach, improves the spectral efficiency. Analytical expressions are derived to predict the BER performances in additive white Gaussian noise channel for both the LPS and HPS channels. Computer simulations are used to show that the system performance of the CSF-SM-DCSK modulation scheme proposed in this work is superior to that of the already published solutions. In addition to the computer simulations, the new chaos-based wireless communications system has been implemented on a wireless open-access research platform to experimentally demonstrate the feasibility and the superiority of CSF-SM-DCSK.

Design and analysis of grouping subcarrier index modulation for differential chaos shift keying communication system

To sufficiently use the subcarrier index modulation in differential chaos shift keying (DCSK) of the recently suggested carrier index differential chaos shift keying (CI-DCSK) and two-layer carrier index differential chaos shift keying (2CI-DCSK), new subcarrier index modulation based DCSK is proposed and named grouping subcarrier index modulation DCSK (GSIM-DCSK). Two grouping subcarrier index modulations based DCSK systems are proposed named GSIM-DCSK-I and GSIM-DCSK-II systems. The data bits are split into L parallel groups, each group has (p1+p2) bits, where p1 bits are used as indexed bits and p2 are used for a modulated bit. The indexed bits are used as an index selector to select one active subcarrier as in GSIM-DCSK-I or inactive subcarrier as in GSIM-DCSK-II out of 2p index subcarriers. While the modulated bits are modulated by DCSK modulation. The bit error rate (BER) of the proposed systems are derived under additive white Gaussian noise and multipath Rayleigh fading channels, respectively. The simulation results are compared with analytical BER and conventional DCSK modulations. Furthermore, the energy efficiency, spectral efficiency, and complexity analysis are derived and compared with the conventional DCSK modulations. The results show that the proposed systems elevate the performance of the conventional DCSK system.

Double-Sub-Stream M-ary Differential Chaos Shift Keying Wireless Communication System Using Chaotic Shape-Forming Filter

An M-ary Differential Chaos Shift Keying modulation using Chaotic Shape-forming Filter (CSF-M-DCSK) is proposed here to transmit two sub-streams with different system performances. The chaotic shape-forming filter is used to generate the chaotic carrier which is modulated according to the DCSK concept. The modulated chaotic signal is demodulated by a coherent matched filter receiver and the maximum likelihood decision rule is used to get the best noise performance. Compared to DCSK and its enhanced versions, the new modulation scheme offers not only better noise and multipath performances but also a higher data rate. The hardware implementation of the proposed method is as simple as that of a conventional communication system. Analytical expressions have been derived for the CSF-M-DCSK Bit Error Rate (BER) and its performance has been evaluated in AWGN and multipath channels by simulations. The new CSF-M-DCSK system has been implemented and successfully tested on a Wireless open-Access Research Platform (WARP). Results of simulations and measurements performed in real application scenarios have proven the feasibility and superiority of CSF-M-DCSK over its competitors.

Design and Analysis of Three-Way Relay Network Coding Schemes Based Differential Chaos Shift Keying Communication System

In this paper, a three-way relay network coding schemes based differential chaos shift keying (DCSK) communication system are investigated. Two schemes of physical layer network coding (PLNC) schemes are proposed to communicate between three users. In the first scheme, three users send their information’s using DCSK modulation in different time slots to the relay, then two encoded bits are extracted from the received bits. After that, the relay broadcast the two encoded bits to three users using DCSK modulation in different time slots. To improve the throughput, energy and spectral efficiency of scheme-1, a new model of PNC scheme is developed based on multiple access DCSK (MA-DCSK) and quadrature chaos shift keying (QCSK) systems. In the first phase, the users send their information’s via MA-DCSK, while in the second phase, the relay broadcast the two encoded bits using QCSK system. In both schemes, the BER analytics are derived and compared with the simulated results under AWGN and multipath Rayleigh fading channel. Furthermore, throughput, link bandwidth and energy efficiency are also derived and compared for two schemes.

A novel chaotic modulation approach of packaged antenna for secured wireless medical sensor network in E‐healthcare applications

AbstractThis article first time reports the chaotic modulation approach toward RF signal processing for secured wireless medical sensor network (WMSN) in E‐healthcare applications. A Lorenz based chaotic modulation approach is implemented which provides lowest bit error rate (BER). The definite analytical expressions for BER in a differential chaos‐shift keying (DCSK) modulation scheme is derived and it predicted good correlation between simulated and theoretical. It is observed that proposed Lorenz chaos‐based DCSK modulation scheme is a potential candidate to provide high security in the patient data for WMSN. An off‐body UWB slotted antenna is designed which could avoid limitation of short‐range distance like implanted ones. The entire work includes numerical, simulated and experimental data in three phases. In first phase, Lorenz chaotic oscillator with electronics compatibility is executed which acts as data acquisition unit and demonstrates two‐dimensional and three‐dimensional chaos attractors. While in the second phase, analysis of BER achieves value of less than 10−4 by providing pseudorandom bit sequence at 5 Gb/s. A chaos modulated envelope using Lorenz based DCSK modulation is obtained by delay element γ. Finally, the third phase is designed on‐wafer off‐body antenna and demonstrates 3.1 to 10.6 GHz UWB toward RF signal processing in E‐healthcare applications.

A Coded DCSK Modulation System Over Rayleigh Fading Channels

Coded modulation (CM) is a bandwidth efficient framework to approach the capacity limit of the differential chaos shift keying (DCSK) systems. In this paper, we propose an M-ary DCSK system operated with CM based on nonbinary protograph low-density parity-check (LDPC) codes over Rayleigh fading channels. First, we investigate the performance of the proposed nonbinary channel coded DCSK (CM-DCSK) and bit-interleaved coded DCSK (BICM-DCSK). In particular, we show that CM-DCSK outperforms BICM-DCSK over Rayleigh fading channels in terms of capacity limit. Compared with BICM-DCSK, CM-DCSK can simplify the receiver structure, since it does not require turbo iteration between the noncoherent detector and channel decoder. Second, guided by the modified extrinsic information transfer (EXIT) analysis, we put forth two new types of nonbinary protograph LDPC codes to approach the capacity limit of CM-DCSK. Both EXIT analysis and simulation results demonstrate that the proposed protograph-coded CM-DCSK achieves a better error performance than BICM-DCSK even with iterative decoding. Furthermore, we show the performance superiority of nonbinary protograph-coded CM-DCSK over a practical ultra-wideband channel. Hence, we conclude that this proposed scheme offers a good alternative for wireless local area network applications.

Performance Improvement of DCSK Modulation in Fading Channels Using Coherent Receiver with Channel Estimation

In this paper, we introduce a differential chaos shift keying (DCSK) with correlator receiver (DCSK-CR) scheme that uses a constant chaotic reference signal for all transmitted symbols. For this scheme, the orthonormal basis signals are completely known at the receiver and a coherent correlator-based structure is used to detect the symbols. Although the performance of a coherent receiver is better than that of a non-coherent receiver, the coherent case needs to know the channel state information to detect symbols in fading channels. Taking the chaotic reference signal constant in the proposed DCSK-CR system helps us to estimate the channel state information for detection. We drive the bit error rate (BER) performance of the proposed system in flat Rayleigh fading channels for both cases of errorless and maximum likelihood (ML) estimation of the channel coefficient. Thanks to the coherent structure, numerical results show that the BER performance of the proposed system outperforms the conventional DCSK case from 3 dB (for the ML case) to 8 dB (for the errorless case) in accordance with the channel estimation accuracy. It is shown that changing the chaotic map, initial condition and the chaotic parameter of the system, does not affect the BER performance of the proposed DCSK-CR, as DCSK. However, in contrast to the DCSK system, changing the spread factor in our system model has no effect on the BER.

Two-Layer Carrier Index Modulation Scheme Based on Differential Chaos Shift Keying

In this paper, a novel carrier index differential chaos shift keying (DCSK) modulation system is proposed for increased energy and spectral efficiencies. The new system splits all data bits into two groups, which are carried by the chaotic signals and their Hilbert transforms, respectively. For each group, one active subcarrier is selected from all candidate subcarriers according to the index bits, and the signal transmitted via the active subcarrier carries one modulated bit through DCSK modulation. By correlating with the exact or the Hilbert filtered chaotic reference signals, the two data groups can be demodulated separately. In each group, the index bits are determined by the maximum energy comparator, while the threshold verdict helps to estimate the modulated bit. Analytical bit error rate expressions over additive white Gaussian noise and multipath Rayleigh fading channels are derived. Simulations and comparisons are also performed to verify the advantages of this new proposed design.

A Differential Chaotic Bit-Interleaved Coded Modulation System Over Multipath Rayleigh Channels

In this paper, a novel differential chaotic bit-interleaved coded modulation (DC-BICM) system is proposed for band-limited transmission. This system combines protograph-based low density parity check codes with constellation-based M-ary differential chaos shift keying (DCSK) modulation by one bitwise interleaving. Bit error rate simulation results show that the system has higher coding gain compared with the constellation-based M-ary DCSK modulation system with the same spectral efficiency over multipath Rayleigh fading channels. At the same time, several simulations and P-EXIT analysis are used to analyze the performance of the proposed system. It is found that there is a lot of room for optimization of the system by comparing decoding thresholds and simulation results. Moreover, the system with only partial channel state information has better performance and lower complexity compared with the traditional bit-interleaved coded modulation (BICM) directsequence-spread-spectrum system. As a result, the DC-BICM system is a good candidate for band-limited transmission.

Performance analysis of differential chaos shift keying modulation with transmit antenna selection

Differential chaos shift keying (DCSK) modulation-based transmit antenna selection (TAS) schemes are proposed to reduce the effect of signal fading with less hardware complexity at the receiver. The transmitter adopts DCSK modulation and employs multiple antennas, whereas the receiver can have single/multiple antennas. On the basis of receiver structure/specifications some TAS schemes are presented. In particular, for multiple transmit antennas and single receive antenna system DCSK-TAS scheme is proposed and for multiple transmit and multiple receive antenna system, two schemes, i.e. DCSK-joint antenna selection and DCSK-TAS/equal gain combining (DCSK-TAS/EGC), are proposed. The probability of error of the proposed schemes is numerically evaluated in the presence of perfect feedback and feedback error in Nakagami- m fading channels. The proposed schemes completely outperform the conventional DCSK scheme with one transmit and one receive antenna. The results show that the DCSK-TAS/EGC has the best error performance among the proposed schemes. Throughput of the proposed schemes is also presented and compared. The error performance of the proposed schemes are numerically evaluated and plotted for the parameters of interest. The simulation results verify the theoretical results.

System Design and Performance Analysis of Orthogonal Multi-Level Differential Chaos Shift Keying Modulation Scheme

A novel non-coherent multi-level differential chaos shift keying (DCSK) modulation scheme is proposed in this paper. This new scheme is based on both the transmitted-reference technique and $M$ -ary orthogonal modulation, where each data-bearing signal is chosen from a set of orthogonal chaotic wavelets constructed by a reference signal. Thanks to this signaling design, the new scheme can achieve a higher attainable data rate, lower energy loss in reference transmission, increased bandwidth efficiency, better data security and better bit error rate (BER) performance as compared to the conventional DCSK. Unlike other DCSK-based systems that separate the reference and data-bearing signals using the TDMA scheme, this new system employs I/Q channels to send these two signals in a parallel and simultaneous manner, making the system easily extendable to multi-carriers. This transmission mechanism not only can further increase data rate but also can remove all radio frequency delay lines from detectors. Analytical BER expressions of the proposed system are derived for both additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels. Relevant simulation results are given and compared to non-coherent binary/ $M$ -ary DCSK systems. In addition, the impacts of various system parameters on noise performance are discussed. Both theoretical analysis and simulation results confirm the promising benefits of the new design.

A Survey on DCSK-Based Communication Systems and Their Application to UWB Scenarios

In the past two decades, chaotic modulations have drawn a great deal of attention in low-power and low-complexity wireless communication applications due to their excellent anti-fading and anti-intercept capabilities. Of particular interest is the differential chaos shift keying (DCSK), which is considered as a very promising chaotic modulation scheme that achieves not only good error performance, but also low implementation complexity. In this treatise, we provide an insightful survey on the state-of-the-art research in DCSK-based communication systems through an extensive open literature search. In doing so, we firstly review the principles of DCSK modulation and the significant milestones since its inception. Subsequently, we introduce meritorious variants of DCSK, all of which can outperform the original one in certain aspects. We also present the joint design guidelines when combining DCSK with other critical techniques, e.g., error-correction coding and cooperative communication, in wireless communications under both single-user and multiaccess scenarios. Besides, we summarize research progress in the application of DCSK-based communication systems to ultra-wideband scenarios and their corresponding advantages. Specifically, we restrict our attention to the relevant modulation and system designs, as well as their performance-analysis methodologies. This survey aims not only to allow researchers understanding the development and current status of DCSK-based communication systems, but also to inspire further research in this area.

BER performance enhancement for secure wireless communication systems based on DCSK-MIMO techniques under Rayleigh fading channel

There has been a growing interest in the use of chaotic techniques for enabling secure communication in recent years. This need has been motivated by the emergence of a number of wireless services which require the channel to provide very low bit error rates (BER) along with information security. As more and more information is transacted over wireless media, there has been increasing criminal activity directed against such systems. This paper investigates the feasibility of using chaotic communications over Multiple-Input-Multiple-Output (MIMO) channels. We have studied the performance of differential chaos shift keying (DCSK) with 2×2 Alamouti scheme and 2×1 Alamouti scheme for different chaotic maps over additive white Gaussian noise (AWGN) and channels disturbed by Rayleigh fading. Both the inherently wideband DCSK modulation and the space-time block code (STBC) are techniques that can mitigate the effect of multipath fading. The use of these schemes allows us to enhance security without degrading the BER performance for Rayleigh fading channels. We have employed an exact method to analyze the performances of DCSK communication system over fading channel. Our simulations indicate that the combination of the STC and tent map provides the best BER performance in addition to security when compared to the choice of other maps. Hence, this study shows that the use of these schemes can allow the user to enhance security without degrading the BER performance while communicating over these channels.

A NOVEL DIFFERENTIAL CHAOS SHIFT KEYING MODULATION SCHEME

In binary Differential Chaos Shift Keying (DCSK), the reference and information bearing chaotic wavelets are transmitted in two consecutive time slots. This TDMA approach provides two independent channels for the transmission of reference and information bearing wavelets but requires a delay component both in the modulator and demodulator circuits, furthermore, it halves the data attainable data rate. The wideband Radio Frequency (RF) delay lines at receiver are extremely difficult to implement with CMOS technology, therefore, the DCSK modulation cannot be exploited in many applications, such as ultra-wideband. To avoid the use of wideband RF delay lines at receiver, an alternative solution is proposed here where both the reference and information bearing wavelets are sent in the same time slot. The two wavelets are separated by Walsh codes instead of time delay. The new modulator and demodulator configurations are given, analytical expressions for the Bit Error Rate (BER) are derived and the derived BER expressions are verified by computer simulations over Additive White Gaussian Noise (AWGN) and multipath Rayleigh fading channels.

Theoretical noise performance of correlator-based chaotic communications schemes

In wireless local area networks and indoor communications, multipath propagation limits the performance of data communications systems. To overcome the multipath propagation problem, a spread spectrum system has to be used. The chaotic communications technique, where inherently wideband chaotic basis functions are used, offers a cheap alternative to conventional spread spectrum communications. Unfortunately, analytic expressions for the noise performance of chaotic modulation schemes are not available in the literature. This has so far prevented a full exploitation of the features of chaotic modulation schemes. By generalizing the waveform communications concept, this paper develops exact expressions for the noise performance of the coherent antipodal chaos shift keying (CSK), coherent differential chaos shift keying (DCSK), and differentially coherent DCSK modulation schemes. We show that the properties of the basis functions have no effect on the noise performance of a modulation scheme, provided that the energy per bit is constant. In this sense, the concept of waveform communications is generalized. Finally, our theoretical results are verified by computer simulations.